EXCHANGE 


C  ' 


A  STUDY  OF  DECOMPOSITION'  PROCESSES' 

APPLICABLE  TO  CERTAIN  PRODUCTS 

OF  COAL  CARBONIZATION 


BY 


MANSION  JAMES  BRADLEY 

A.  B.  McMaster  University,  1915 
A.  M.  McMaster  University,  1915 


THESIS 

v 

Submitted  in  Partial  Fulfillment  of  the  Requirements  for  the 

Decree  of 

DOCTOR  OF  PHILOSOPHY 
IN  CHEMISTRY 

IN 

THE  GRADUATE  SCHOOL 

OF  THE 

/ 

UNIVERSITY  Olf  ILLINOIS 
1921 

REPRINTED  FROM  CHEMICAL  AND  METALLURGICAL  ENGINEERING 
Vol.  27,  No.  15.  Oct.  n,  1922 


A  STUDY  OF  DECOMP(^lfl6N'PROC!E^siE:S 

APPLICABLE  TO  CERTAIN  PRODUCTS 

OF  COAL  CARBONIZATION 


BY 


MANSION  JAMES  BRADLEY 

A.  B.  McMaster  University,  1915 
A.  M.  McMaster  University,  1915 


THESIS 

Submitted  in  Partial  Fulfillment  of  the  Requirements  for  the 

Decree  of 

DOCTOR  OF  PHILOSOPHY 

IN  CHEMISTRY 

IN 

THE  GRADUATE  SCHOOL 

OF  THE 

UNIVERSITY  OF  ILLINOIS 
1921 

REPRINTED  FROM   CHEMICAL  AND  METALLURGICAL  ENGINEERING 
Vol.  27,  No.  15.  Oct.  n,  1922 


4s- 


ACKNOWLEDGMENT 

The  writer  wishes  to  express  his  sincere  thanks  to  Prof.  5.  \V. 
Pan%  whose  _  assistance,  guidance  and  encouragement 

made  this  thc:  Deep  appreciation  is  felt  for  the  valuable 

training  in  the  fundamentals  of  research.  It  is  expected  that  this 
stimulated  appreciation  of  chemical  investigation  will  increase  with 
time  because  research  is  appreciation. 

He  also  wishes  to  thank  Dr.  T.  E.  Layng,  not  only  for  help 
and  instruction  in  assembling  the  apparatus,  but  more  especially  for 
the  many  valuable  suggestions  and  advice  during  the  investigation. 


H    print. (<    from    C'hemii-al    ami     .Mr  taJlursi«-i*l 
Vol.    t~t      No.    I.V    <»«•!.    11.     I9^i 


Decomposition  Processes 

Applicable  to  Certain  Products 

Of  Coal  Carbonization 

An  Experimental  Study  in 
Which  Mixed  Xylenes  Were 
Decomposed  Under  Varied  Con- 
ditions of  Temperature,  Pres- 
sure and  Atmosphere — Effects 
of  Different  Contact  Surfaces- 
Identification  of  Many  of  the  Im- 
portant Decomposition  Products 

BY  M.  J.  BRADLEY-  WITH  S.  W.  PARR 

THE  extensive  experimental  work  carried  on  in 
these  laboratories  on  the  coking  of  Illinois,  East- 
ern bituminous,  Utah.  Canadian  and  many  other 
coals  has  demonstrated  the  possibility  of  increasing  the 
yield  of  tar  oils  approximately  one  hundred-fold,  de- 
pending upon  the  variety  of  coal  used  in  the  low-tem- 
perature carbonizing  process.  The  distillate  obtained 
in  this  manner  contains  a  large  quantity  of  flHHR. 
low-boiling,  aromatic  oils,  some  of  which  under  normal 
commercial  conditions  have  a  limited  application  in  the 
industries.  For  instance,  xylene  could  be  obtained  in 
large  quantities  even  under  present  conditions,  if  its 
industrial  demand  were  such  as  to  warrant  the  expense 
of  recovery  and  purifying.  This  hydrocarbon,  having 
a  boiling  range  from  137  to  141  deg.  C..  has  too  low  a 
vapor  pressure  to  be  an  efficient  motor  fuel,  but  if  by 
pyrogenic  decomposition  it  can  be  converted  into  ben- 
zene, which  boils  at  80  deg.  C.,  its  value  as  a  motor  fuel 
is  greatly  increased.  Xylene  can  also  be  decomposed  in 
such  a  manner  as  to  form  higher  boiling  compounds, 
many  being  solids  at  ordinary  temperatures.  Anthra- 

*An  abstract  of  work  carried  out  by  M.  J.  Bradley  in  partial 
fulfillment  for  the  de.srree  of  Doctor  of  Philosophy  at  the  Univer- 
sity of  Illinois. 

[3] 


'eene  'and*<met^yV-ahlhracenes  can  be  obtained  in  this 
manner,  but,  by  known  methods,  in  small  yields. 

In  this  research  an  endeavor  was  made  to  find  out 
the  mode  of  decomposition  and  formation  of  the  various 
products  obtained  from  xylene  in  order  to  be  able  to 
increase  the  yields  of  the  desired  compounds,  and  if 
possible  to  use  this  knowledge  in  working  over  crude 
tar  oils  in  order  to  obtain  similar  products.  In  the 
following  experimental  work  some  striking  results  were 
obtained  which  seemed  to  be  directly  opposed  to  those 
recorded  by  other  investigators.1  Pure  xylene  was 
passed  through  an  electrically  heated  furnace,  at  various 
temperatures,  under  different  pressures  and  in  the  pres- 
ence of  such  contact  surfaces  as  iron  oxides,  reduced 
iron,  copper,  tin,  molybdenum,  chromium,  the  alloy 
Illium,  aluminum,  nickel,  cobalt,  manganese,  charcoal, 
pumice  and  refractory.  The  condensible  compounds  were 
collected,  weighed  and  analyzed  and  the  non-condensible 
measured  and  analyzed.  The  vapor  condition  inside  of 
the  furnace  was  varied  by  introducing,  at  the  same 
time  with  the  xylene,  air,  superheated  steam,  carbon 
dioxide,  carbon  monoxide,  hydrogen,  nitrogen  or 
ethylene. 

APPARATUS  USED  IN  EXPERIMENTAL  WORK 

The  essential  parts  of  the  apparatus  are  shown  in 
the  photographs  accompanying  this  paper.  The  com- 
plete outfit,  being  of  a  conventional  type,  requires  little 
explanation,  with  the  possible  exception  of  the  furnace. 
It  was  made  by  taking  6  ft.  of  4-in.  wrought-iron  pipe, 
threading  on  flanges  and  thermocouple  pockets  and  then 
having  these  joints  acetylene-welded  to  insure  having 
no  leaks  under  conditions  of  high  temperature  and  pres- 
sure. The  caps  were  cast  particularly  for  this  furnace 
and  extended  li  in.  into  the  end  of  the  pipe  and  were 
fitted  with  three  f-in.  threaded  openings  leading  into 
the  furnace. 

The  pipe  was  thinly  coated  with  alundum  cement, 
wound  in  five  sections,  each  having  36.5  ft.  of  nickel- 
chromium  resistance  wire,  and  again  coated  with 
cement.  It  was  surrounded  by  a  wooden  box,  20  in. 
square  and  as  long  as  the  furnace,  which  contained 
the  pulverized-asbestos  and  Sil-0-Cel  insulation.  Each 


*In  order  to  conserve  space,  no  discussion  of  other  investiga- 
tions is  included  in  this  paper,  but  a  list  of  articles  on  the  pyro- 
genic  reactions  of  aromatic  hydrocarbons  which  appeared  to  be 
most  important  in  connection  with  the  present  problem  is  given 
at  the  end. 

[4] 


heating  element,  when  connected  directly  across  the 
110-volt  line,  permitted  a  maximum  current  of  20 
amperes  to  pass  through,. but  this  could  be  reduced  to 
5  amperes  by  means  of  an  external  resistance  con- 
nected in  series  at  the  switchboard.  At  no  time  was 
more  than  10  amperes  permitted  to  go  through  the 
heating  elements.  By  this  means  the  heat  of  the  fur- 
nace could  be  kept  constant  at  any  desired  temperature 
between  250  and  900  deg.  C. 

The  top  end  was  fitted  with  feed  pipes  for  xylene, 
superheated  steam  and  other  gases,  also  with  a  pressure 
and  reduced  pressure  gage.  On  the  exit  at  the  bottom 
end  was  a  safety  relief  valve,  or  constant  pressure  valve, 
which  could  be  adjusted  to  let  the  gases  escape  into  the 
line  leading  to  the  gas  meter  at  any  desired  pressure. 


FIG.  1 — UPPER  END  OP  FURNACE 

This  outfit  has  been  operated  at  pressures  as  high  as 
180  Ib.  per  square  inch.  The  temperature  was  meas- 
ured by  means  of  a  thermocouple.  The  cold  junction 
was  kept  at  zero  by  means  of  a  Thermos  bottle  well  and 
ice  water,  and  the  e.m.f.  was  read  on  a  millivoltmeter 
which  had  been  standardized  at  known  temperatures. 
By  this  method  the  temperature  could  be  read  accu- 
rately within  4  or  5  deg.  The  thermocouple  pockets  K 
(see  Figs.  1  and  2)  extended  into  the  middle  of  the 
furnace  and  thus  gave  the  temperature  of  the  area 
where  the  largest  volume  of  vapors  passed. 

[5] 


FIG.   2— LOWER  END  OF  THE  FURNACE 


METHOD  OF  OPERATION 

The  mechanical  arrangement  of  the  apparatus  is  ap- 
parent from  the  explanation  of  the  progressive  steps 
of  a  typical  run.  The  xylene  was  placed  in  the  reser- 
voir A  (Figs.  1  and  2),  fed  by  means  of  a  regulating 
valve  through  the  sight-glass  or  bypass  B  into  the  upper 
end  of  the  furnace  C.  Here  also  could  be  introduced 
gas,  such  as  hydrogen,  nitrogen,  carbon  dioxide  or 
ethylene,  from  the  cylinder  7  or  steam  from  the  high- 
pressure  steam  line  J  could  be  introduced  through  the 
gas-fired  superheater  H.  Another  attachment,  not 
shown  in  the  illustration,  permitted  the  use  of  com- 
pressed air. 

In  passing  down  through  C  the  vapors  came  in  con- 
tact with  the  various  contact  surfaces  used.  The  high- 
est boiling  condensate  was  collected  in  receiver  7,  the 
medium  oils  in  No.  2,  while  the  gases,  after  passing 

[6] 


through  the  water-cooled  condensers  D,  were  scrubbed 
with  heavy  oil  in  receiver  3.  The  gas  leaving  receiver  3 
passed  through  pipe  E  to  be  measured  by  the  meter  F 
and  was  then  burned,  or  analyzed  by  means  of  the  modi- 
fied Orsat  apparatus  G. 

When  running  under  increased  pressure,  extra  lengths 
of  piping,  fitted  with  a  gate  valve,  were  attached  to  the 
ends  of  the  condensers.  By  keeping  the  lower  valve 
closed  and  the  upper  one  open,  the  condensate  collected 
between  them  and  could  be  easily  removed,  by  closing 
the  upper  valve  and  opening  the  lower  one,  without 
causing  any  change  in  the  pressure  within  the  furnace. 

METHOD  OF  ANALYZING  PRODUCTS 

The  condensible  products  were  weighed,  fractionated 
through  a  6-in.  wash  column  of  glass  beads  until  all  the 
liquids  boiling  below  145  deg.  C.  were  removed.  The 
liquid  boiling  above  145  deg.  C.,  designated  in  the 
following  results  as  high-boiling  product,  was  then 
transferred  to  an  ordinary  distilling  flask  and  the  frac- 
tionation  continued  until  all  but  coke  was  driven  over. 
These  operations  were  carried  out  in  electrically  heated 
pot  furnaces  built  to  accommodate  the  particular  flask 
used  and  maintained  at  a  constant  temperature  by 
means  of  external  resistances.  Thus  each  furnace  could 
be  regulated  so  that  no  distillate  would  be  driven  over 
above  a  certain  temperature.  One  furnace  was  used  for 
each  cut,  up  to  105  deg.  C.;  from  105  deg.  C.  to  130 
deg.  C. ;  from  130  deg.  C.  to  145  deg.  C. ;  and  finally  one 
for  the  higher  boiling  compounds.  This  method  saved 
much  time,  as  it  was  possible  to  have  several  fraction- 
ating flasks  going  at  the  same  time  as  the  furnace  and 
gas  analyses. 

The  solids  obtained  from  the  high-boiling  oils  were 
purified  and  analyzed  by  a  combination  of  various  meth- 
ods as  described  by  Charlton  (17),  Clark  (21),  Cook  (22) 
and  others  (see  bibliography  at  end  of  article).  Partial 
separation  was  obtained  by  making  the  distillation  cuts 
at  various  temperatures  and  then  lowering  the  tem- 
perature sufficiently  to  freeze  out  the  solids.  In  some 
cases  steam  distillation,  fractional  solution,  class  reac- 
tions and  other  methods  were  used  to  advantage,  but 
these  operations  are  too  long  to  be  described  in  this 
paper. 

The  products  not  removed  in  the  scrubbing  process 
were  measured  by  a  standard  wet  meter  and  then 
burned.  The  sample  taken  for  analysis  was  collected 

[7] 


before  passing  through  the  meter.  The  gases  were 
analyzed  by  means  of  a  modified  Orsat  apparatus  con- 
structed by  the  author.  It  is  shown  in  Fig.  3  with 
the  oxygen  and  nitrogen  reservoir  permanently  attached 
to  the  manifold  ready  for  use  and  the  furnace  removed, 
showing  the  copper  oxide  tube.  Another  modification 
of  this  apparatus  is  shown  in  a  text2  describing  a  num- 
ber of  processes  and  apparatus  developed  in  this  labora- 
tory. The  carbon  dioxide  was  removed  with  35  per  cent 
KOH  solution;  oxygen  by  potassium  pyrogallate; 
acetylene  by  ammoniacal  silver  chloride;  ethylene  by 
bromine  water;  aromatics  by  20  per  cent  fuming  sul- 
phuric acid ;  hydrogen  and  carbon  monoxide  by  com- 
bustion with  copper  and  eerie  oxides;  ethane  and 
methane  by  slow  combustion  by  means  of  a  platinum 
coil  in  pure  oxygen;  and  the  nitrogen  was  estimated 
by  difference. 

The  gas  sample  was  taken  in  at  the  top  of  the 
burette  and  measured  at  atmospheric  pressure  by  means 
of  twin  burettes  joined  at  bottom.  The  copper  oxide 

2S.  W.  Parr,  "The  Analysis  of  Fuel,  Gas,  Water  and  Lubricants," 
3rd  edition,  1922,  McGraw-Hill  Book  Co.,  Inc.,  New  York  City. 


FIG.    3— MODIFIED      ORSAT   GAS   ANALYZING  APPARATUS, 
SHOWING    THE   WATER-COOLED    FURNACE   REMOVED 


[8] 


tube  was  made  of  Pyrex  glass  and  contained  about  30 
grams  of  granular  copper  oxide  which  passed  through 
a  10-mesh  and  remained  on  a  20-mesh  screen.  To  this 
was  added  about  0.9  gram  of  finely  powdered  eerie 
oxide,  which  seemed  to  activate  the  copper  oxide  and 
greatly  to  hasten  the  combustion  of  hydrogen.  In  fact, 
where  the  carbon  monoxide  content  was  low  or  pre- 
viously removed  by  acid  cuprous  chloride,  70  to  80  c.c. 
of  hydrogen  could  easily  be  completely  burned  in  5 
minutes.  In  the  presence  of  considerable  quantities  of 
carbon  monoxide  the  combustion  was  slower.  The  com- 
bustion tube  was  frequently  oxidized  with  pure  oxygen. 
The  absorption  pipettes  contained  thin-walled  glass 
tubing  to  give  surface  and  speed  up  the  absorption. 
The  slow  combustion  pipette  for  ethane  and  methane 
was  made  from  a  300-c.c.  thick-walled  Kjeldahl  Pyrex 
flask,  which  proved  very  satisfactory.  The  tempera- 
ture of  the  platinum  coil  was  regulated  by  means  of  a 
chromel  resistance  in  series  shown  on  the  front  of  the 
stand.  It  is  realized  that  an  exact  separation  of  acety- 
lene and  ethylene  cannot  be  obtained  in  the  above  man- 
ner, but  by  leaving  the  gases  in  contact  with  the 
ammoniacal  silver  chloride  solution  during  a  constant 
time  interval  in  each  analysis,  a  relative  idea  of  the 
two  constituents  can  be  obtained.  The  complete  analysis 
could  be  made  in  this  apparatus  in  less  than  30  minutes. 

SPECIFICATION  OF  THE  HYDROCARBONS 

The  mixed  xylene,  which  was  the  commercial  product 
such  as  is  usually  marketed  in  10-gal.  cans,  was  used  in 
the  major  portion  of  this  work.  After  redistilling,  it 
was  water-white,  contained  no  suspended  material,  was 
free  from  moisture,  had  no  foreign  odor,  practically  all 
distilled  over  between  137  and  142  deg.  C.  and  had  a 
specific  gravity  of  0.8664  at  15.5  deg.  C. 

The  benzene,  toluene  and  naphthalene  used  were  the 
commercial  product  in  stock  in  the  chemistry  storeroom. 
They  were  not  analyzed  or  purified  in  any  manner,  as 
only  a  few  runs  were  made  with  them  to  compare  with 
the  results  obtained  on  xylene  under  similar  conditions. 

The  results  on  the  decomposition  of  xylene  are  sum- 
marized in  Table  I  and  the  outstanding  features  are 
discussed  briefly  in  the  comments  on  each  series. 

RESULTS  OF  TESTS 

Each  run  selected  for  use  in  the  table  is  a  typical 
result  obtained  in  a  series  of  eight  to  twelve  similar 

[9] 


runs  made  while  the  furnace  was  heated  up  and  with 
similar  conditions  inside  the  furnace — that  is,  as  to 
contact  surfaces  and  lining.  The  results  are  given  as 
obtained  for  various  temperature  ranges,  different  pres- 
sures and  under  the  influence  of  other  gases  which 
were  introduced  into  the  furnace  at  the  same  time  as 
the  xylene.  The  amount  of  xylene  used  was  1,000, 
500  or  200  grams  and  was  fed  through  the  furnace  in 
2-hour  or  1-hour  periods.  The  sample  of  gas  for  anal- 
ysis was  taken  when  the  run  was  about  three-quarters 
completed.  The  loss  in  per  cent  is  given  on  the  basis 
of  the  weight  of  the  original  xylene;  the  different 
fractions  of  the  condensate  and  coke  obtained  are  given 
on  the  same  basis.  The  results  tabulated  for  fractions 
boiling  above  145  deg.  C.  are  not  given  on  a  particular 
run,  but  on  heavy  boiling  product  obtained  in  several 
runs  in  the  same  series. 

A  number  of  preliminary  runs  between  200  and  600 
deg.  C.  at  50  deg.  C.  intervals  were  made  on  1,000-gram 
samples  of  xylene  to  see  if  the  iron  surface  of  the 
furnace  would  promote  any  reactions.  The  loss  was  less 
than  1  per  cent  and  the  volume  of  gas  was  so  small  that 
it  was  not  analyzed;  the  condensate  was  practically  un- 
changed xylene. 

CHARCOAL  AS  A  CATALYST 

For  series  1,  No.  26  being  a  sample,  2  kg.  of  wood 
charcoal,  cut  in  small  cubes  about  I  in.  square,  were 
placed  inside  of  the  furnace.  The  first  run  was  made  at 
250  deg.  C.,  but  no  appreciable  reactions  were  noted. 
As  the  temperature  rose,  more  gas  was  given  off  and 
contained  increasing  amounts  of  CO.  Xylene  seemed 
very  stable  under  these  conditions  up  to  temperatures 
above  650  deg.  C.,  when  about  one-fourth  of  it  was 
lost.  At  lower  temperatures  considerable  ethane  was 
found  in  the  escaping  gas,  while  the  proportion  of 
methane  was  small.  At  600  deg.  C.  the  ethane  content 
was  at  its  maximum,  about  7.5  per  cent,  and  with  20.0 
per  cent  of  methane  present,  but  as  the  temperature 
rose,  the  ethane  decreased  rapidly,  while  the  percentage 
of  methane  increased.  On  the  conclusion  of  the  series, 
considerable  carbon,  from  the  decomposition  of  xylene, 
was  found  adhering  to  the  furnace  walls. 

Before  commencing  series  2,  the  furnace  was  cleaned 
by  means  of  a  wire  brush  and  2  kg.  of  new  charcoal 
cubes  inserted.  To  insure  against  leaks,  the  furnace 
was  subjected  to  125  Ib.  pressure  of  live  steam  before 

[10] 


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lllSIIMdSSItffSSo^ll^^lsSSii 
[ii] 


heating  up.  This  steaming  of  the  charcoal  seemed  to 
activate  it  so  the  reactions  commenced  at  lower  tem- 
peratures, for  instance  at  550  deg.  C.  over  20  per  cent 
ethane  was  found  in  the  outgoing  gas  and  about  25  per 
cent  of  the  condensate  was  toluene.  At  600  deg.  C. 
the  ethane  had  disappeared  and  the  toluene  fraction 
decreased,  while  the  hydrogen  and  methane  were  greatly 
increased.  During  the  run  at  700  deg.  C.  the  tempera- 
ture of  the  furnace  fell  rapidly  and  a  great  increase 
in  the  volume  of  gases  took  place.  The  furnace  became 
activated  in  such  a  manner  that  the  xylene  was  com- 
pletely decomposed  into  gaseous  products  and  amorphous 
carbon.  Run  33  summarizes  the  results.  Several  other 
runs  at  lower  temperatures  gave  similar  products ;  even 
introducing  hydrogen  from  a  cylinder  at  various  pres- 
sures up  to  150  Ib.  did  not  stabilize  the  reactions  in  such 
a  way  as  to  obtain  any  condensate.  The  xylene  was 
completely  decomposed  into  hydrogen,  methane  and 
carbon. 

EFFECTS  OF  OXYGEN  AND  HYDROGEN 
Before  beginning  series  3  about  8  cu.ft.  of  air  was 
passed  through  the  heated  furnace ;  approximately  14 
per  cent  of  C02  was  found  in  the  issuing  gases.  The 
air  poisoned  or  deadened  the  activity  of  the  furnace, 
with  the  result  that  44  per  cent  of  the  xylene  was 
unchanged  at  500  deg.  C.  The  air  was  discontinued 
during  run  50.  In  this  series  it  was  found  that  char- 
coal, when  heated  to  700  deg.  C.  under  reducing  condi- 
tions and  then  cooled  out  of  contact  with  air,  would, 
at  ordinary  temperatures,  take  up  air  readily.  On  again 
heating,  the  oxygen  came  off  as  carbon  oxides,  the 
dioxide  at  lower  and  the  monoxide  at  higher  tempera- 
tures. It  was  extremely  difficult  to  remove  the  oxygen 
even  at  700  deg.  C.  in  the  presence  of  hydrogen,  dimin- 
ishing amounts  being  given  off  after  several  days' 
treatment. 

Before  series  4  the  furnace  had  been  thoroughly 
cleaned  of  carbon  and  new  charcoal  added.  While  heat- 
ing up  it  was  kept  under  reducing  conditions  with 
hydrogen  from  a  cylinder.  During  this  series  consider- 
able toluene  was  formed,  especially  at  650,  700  and 
750  deg.  C.  At  the  latter  temperature,  under  excess 
hydrogen  from  the  cylinder,  a  yield  of  56  per  cent  was 
obtained,  while  without  the  hydrogen  only  43  to  45  per 
cent  was  obtainable.  In  this  case  hydrogen  seemed  to 

[12] 


stabilize    rather    than    promote    the    decomposition    of 
toluene.     Superheated  steam  deadened  the  activity  of 
the  furnace  in  such  a  way  as  to  stabilize  the  xylene 
passing   through,   although   after    steaming    and  then 
reducing  for  a  short  time  the  furnace  became  activated 
in  such  a  manner  as  to  decompose  the  xylene  completely. 
This  was  also  found  to  be  true  without  any  charcoal 
in  the  furnace.     That  is,  the   iron  surfaces  could  be 
freshly  oxidized  or  activated  by  means  of  steam  when 
heated  between  600  and  790  deg.  C.  and  after  reducing 
slightly  became  activated  so  that  the  xylene  was  com- 
pletely decomposed  into  carbon,  hydrogen  and  methane. 
Run  61  shows  the  results  of  the  first  run  after  passing 
superheated  steam  through  the  furnace;  after  reducing 
with  hydrogen  for  a  short  time,  the  xylene  was  com- 
pletely decomposed,  but  could  be  partly  stabilized  by 
passing  CO  or  C02  into  the  furnace  at  the  same  time 
as  the  hydrocarbon.    Hydrogen  even  at  140  Ib.  pressure 
did  not  stabilize  any  of  the  liquid  products,  once  the 
furnace  was  in  this  activated  condition.     The  carbon 
deposited  was  intensely  black  and  fluffy,  contained  some 
small  percentage  of  liquid  hydrocarbon  and  about  11 
per  cent  of  iron,  which  was  found  to  be  a  mixture  of 
the  magnetic  oxide  and  other  oxides,  along  with  very 
small  particles  of  finely  divided  metallic  iron.     It  was 
impossible  to  tell  from  these  results  whether  it  was  the 
iron  or  the  charcoal  surfaces  which  was  causing  the 
complete  decomposition  of  the  liquid  hydrocarbons. 

EFFECT  OF  METAL  FURNACE  WALL 

In  series  5  a  lining  tube  of  No.  18  sheet  copper  was 
placed  snugly  in  the  furnace  so  that  no  iron  surfaces 
were  left  exposed.  Copper  seemed  to  have  a  tendency 
to  decompose  xylene  into  lower  rather  than  higher 
boiling  compounds,  as  shown  in  run  78.  Oxidizing  the 
copper  made  it  somewhat  more  active,  but  on  reducing 
it  again  complete  decomposition  of  the  xylene  did  not 
take  place.  What  decomposition  did  take  place  seemed 
to  form  liquid  and  gaseous  products  rather  than  amor- 
phous carbon,  which  was  formed  only  in  extremely  small 
amounts. 

In  series  6  the  furnace  was  copper  lined  and  con- 
tained 24  kg.  of  charcoal  cubes.  Typical  results  ob- 
tained in  this  series  is  shown  in  run  88.  The  reactions 
below  600  deg.  C.  were  unimportant,  but  as  the  tem- 
perature rose  the  loss  became  greater.  The  loss  was 
cut  down  somewhat  by  introducing  hydrogen  into  the 

[13] 


furnace,  which  appeared  to  stabilize  and  increase  the 
toluene  fraction.  However,  it  was  found  impossible  to 
activate  the  furnace  and  charcoal  as  described  for 
series  2  and  3. 

In  series  7  the  furnace  was  copper  lined  and  the  con- 
tact surface  consisted  of  3i  kg.  of  oxidized  Illium  turn- 
ings, mechanically  mixed  among  small  pieces  of  pumice. 
These  runs  demonstrated  that  around  700  deg.  C.  the 
decomposition  of  xylene  was  greatest  and  giving  the 
maximum  quantity  of  the  lower  boiling  fractions. 

Series  8  was  made  over  small  pieces  of  pumice  which 
had  been  dipped  in  nickel  nitrate  and  then  reduced  at 
500  deg.  C.  with  hydrogen.  This  was  to  get  the  metal 
in  a  finely  divided  condition  and  over  as  much  surface 
as  possible.  Several  runs  were  made  between  500  and 
800  deg.  C.,  run  104  being  a  sample.  Nickel  under 
these  conditions  did  not  promote  the  formation  of  liquid 
products,  but  rather  favored  complete  decomposition  of 
the  hydrocarbons  into  hydrogen,  methane  and  carbon. 
In  fact,  the  deposited  carbon  soon  filled  the  furnace  so 
that  the  series  had  to  be  discontinued.  At  this  time  the 
copper  lining  was  found  to  have  become  broken  in  sev- 
eral places,  leaving  iron  surfaces  exposed,  which  no 
doubt  had  influenced  the  reactions. 

Before  commencing  series  9  the  furnace  was  relined 
with  tinned  copper,  the  tin  surface  being  on  the  inside. 
Run  113  gives  a  typical  example  of  results  obtained. 
The  series  seemed  to  indicate  that  in  the  neighborhood 
of  700  deg.  C.  tin  promoted  the  formation  of  low-boiling 
liquids.  No  other  contact  materials  were  in  the  furnace 
during  these  runs. 

EFFECT  OF  NICKEL,  MOLYBDENUM  AND  COBALT 

Series  10  was  run  through  the  tinned-copper  lining 
and  using  2£  kg.  of  charcoal  cubes  which  had  been 
dipped  in  a  thin  paste  of  nickel  oxide  and  dried  at  110 
deg.  C.  In  this  case  the  nickel  oxide  and  furnace  were 
not  reduced  before  commencing  the  runs.  The  results 
obtained  were  similar  to  those  of  the  iron-charcoal 
series — that  is,  the  xylene  tended  to  be  completely 
broken  down  into  carbon,  hydrogen  and  methane.  Even 
at  as  low  a  temperature  as  450  deg.  C.,  83.5  per  cent 
total  loss  was  obtained.  During  run  125  hydrogen  was 
introduced  at  15  Ib.  pressure,  but  did  not  stabilize  any 
of  the  liquid  hydrocarbons.  Small  amounts  of  water 
were  collected  in  the  condensate  in  every  run.  The 
furnace  was  soon  choked  up  by  the  deposited  carbon. 

[14] 


During  this  series  practically  all  the  tin  surface  scaled 
off  the  copper  lining. 

The  next  series,  No.  11,  was  run  in  the  copper-lined 
furnace  after  over  £  Ib.  of  metallic  molybdenum  powder 
had  been  scattered  among  the  small  pieces  of  pumice 
stone.  As  in  the  preceding  series,  considerable  moisture 
was  collected  in  the  condensate.  No  appreciable  decom- 
position of  the  xylene  took  place  below  600  deg.  C.,  but 
above  this  temperature  the  reactions  greatly  favored 
the  formation  of  benzene  and  of  methane  rather  than 
hydrogen  and  carbon.  Run  133  gives  a  fair  idea  of 
results  obtained. 

Series  13  was  run  with  the  copper-lined  furnace  con- 
taining 5  kg.  of  1-cm.  cobalt  cubes.  To  reduce  all  the 
oxide  surfaces  the  furnace  was  heated  to  500  deg.  C. 
and  maintained  under  60  Ib.  pressure  of  hydrogen  for 
several  hours.  Even  after  this  treatment  moisture  was 
collected  in  the  condensate.  Cobalt  promotes  the  decom- 
position of  xylene  at  low  temperatures;  even  at  450 
deg.  C.  about  35  per  cent  was  lost,  and  at  550  to  575 
deg.  C.  considerable  toluene  was  formed,  as  shown  in 
run  142. 

MANGANESE  AND  ALUMINUM 

In  series  14  manganese  in  a  fine  powder  was  scat- 
tered among  the  small  pieces  of  pumice  stone.  This 
metal  promoted  the  decomposition  of  xylene  at  lower 
temperatures  than  any  tried  previously  and  the  products 
formed  were  liquid  rather  than  gaseous.  Run  151  indi- 
cates the  decomposition  products  obtained. 

In  series  15,  440  grams  of  aluminum  powder  was 
scattered  among  the  small  pieces  of  pumice  stone  and 
several  runs  were  made  at  various  temperatures. 
Below  600  deg.  C.  very  little  decomposition  of  xylene 
took  place,  but  what  was  changed  went  to  hydrogen  and 
deposited  carbon.  Run  163,  at  680  deg.  C.,  indicates 
that  aluminum  does  not  favor  the  formation  of  higher 
boiling  compounds  from  xylene.  It  should  be  mentioned 
that  the  copper  lining  during  this  series  had  given  way 
in  several  places  so  that  some  iron  was  exposed. 

Before  series  16  the  copper  lining  was  removed  from 
the  furnace,  the  latter  cleaned  by  means  of  a  wire  brush, 
reduced  while  hot  with  hydrogen  and  when  cold  was 
coated  with  a  lining  made  by  mixing  80  per  cent 
Hytempite  with  20  per  cent  alundum  cement.  After 
drying  and  baking,  several  runs  were  made  without 
other  contact  surfaces.  Under  these  conditions  the 

[15] 


xylene  did  not  decompose  much  below  600  deg.  C.,  while 
above  this  temperature  liquids  rather  than  gaseous  com- 
pounds were  formed.  Run  167  gives  results  at  550  deg. 
C.  and  shows  the  amount  of  ethylene  formed. 

CRACKING  IN  ATMOSPHERE  OF  ETHYLENE 

For  series  20  a  cylinder  of  commercial  ethylene  was 
connected  to  the  upper  end  of  the  furnace.  The  refrac- 
tory lining  was  in  good  repair  and  no  other  materials 
were  introduced  for  contact  surfaces.  The  preliminary 
runs  introducing  ethylene  at  45  Ib.  pressure  into  the 
furnace  gave  some  interesting  data  regarding  the  stabil- 
ity of  ethane,  methane  and  ethylene  under  these  con- 
ditions. At  415  deg.  C.  the  waste  gases  contained  89.4 
per  cent  of  ethylene,  no  ethane  and  8.5  per  cent  of 
methane;  at  475  deg.  C.  it  contained  73.9  per  cent  of 
ethylene,  4.6  per  cent  of  ethane  and  10.0  per  cent  of 
methane.  The  maximum  amount  of  ethane  was  ob- 
tained at  500  deg.  C. ;  the  methane  increased  with 
temperature,  and  at  675  deg.  C.  the  outgoing  gases 
contained  84.1  per  cent  of  methane.  Below  475  deg.  C. 
very  little  decomposition  of  xylene  took  place,  the  loss 
being  less  than  5  per  cent.  In  the  runs  below  475  deg. 
C.  there  was  always  a  gain  in  weight  in  the  liquid 
condensate,  although  little  xylene  was  decomposed.  This 
was  found  to  be  due  to  the  xylene  dissolving  considerable 
volumes  of  the  ethylene,  which  was  readily  given  off 
when  redistilling.  Around  600  deg.  C.  the  furnace  de- 
composed xylene  and  ethylene  very  rapidly,  the  latter 
going  principally  to  methane.  In  order  to  keep  the 
furnace  atmosphere  mostly  ethylene,  the  pressure  out- 
let gage  was  set  at  2  Ib.  and  the  ethylene  introduced 
into  the  furnace  very  rapidly.  Under  these  conditions 
the  maximum  yield  of  high-boiling  compounds  was  ob- 
tained. The  results  are  given  in  run  286.  Many  other 
runs  under  various  conditions  of  pressure,  rates  of  feed 
and  gaseous  atmospheres  were  made,  but  the  percent- 
age of  higher  boiling  compounds  were  lower  than  in 
the  run  tabulated. 

In  series  21  the  refractory-lined  furnace  was  found 
to  decompose  xylene  as  described  for  series  16.  It 
was  now  desirable  to  see  if  the  lower  boiling  liquids 
could  be  stabilized  by  deliberate  control  of  the  gaseous 
atmosphere  inside  the  furnace.  In  run  287  the  fur- 
nace was  maintained  under  125  Ib.  pressure  with  hydro- 
gen from  a  cylinder  while  the  xylene  was  being 
introduced.  The  results  indicate  that  the  major  portion 

[16] 


of  the  xylene  was  decomposed  into  lower  boiling  liquids. 
In  series  25  the  low-boiling  liquids  were  slightly  in- 
creased by  increasing  the  hydrogen  concentration  in 
the  furnace.  The  maximum  yield  is  shown  in  run  288. 
This  result  is  calculated  from  the  weight  of  xylene 
used,  while  by  referring  to  the  equation  C8H10  + 
2H2  ^  2CH4  +  C6H6,  it  is  evident  that  this  would  equal 
about  93.7  per  cent  of  the  possible  theoretical  yield.  The 
carbon  deposited  in  these  runs  was  very  different  in 
appearance  from  that  described  previously.  It  was  a 
metallic  gray  color  and  was  granular  or  sandy,  while 
the  other  deposits  had  been  intensely  black  and  slightly 
oily. 

RUNS  USING  BENZENE,  TOLUENE  AND  NAPHTHALENE 

The  runs  with  benzene  were  made  through  the  iron 
furnace  containing  24  kg.  of  charcoal,  the  purpose  being 
to  try  to  check  the  results  of  Cobb  and  Rollings  (23). 
They  found  that  benzene  passing  through  coke  heated  to 
800  deg.  C.  could  be  entirely  stabilized  by  means  of  ex- 
cess hydrogen.  In  these  experiments  it  was  found  that 
when  the  charcoal  and  furnace  were  activated  it  was 
impossible  to  stabilize  the  benzene  even  at  500  deg.  C. 
Pressures  as  high  as  125  Ib.  of  hydrogen  per  square 
inch  were  used.  On  the  other  hand,  if  the  charcoal  and 
furnace  had  been  treated  with  superheated  steam,  air 
or  carbon  dioxide,  benzene  could  be  entirely  stabilized 
at  temperatures  as  high  as  800  deg.  C.  with  very  small 
pressures  of  hydrogen. 

Cobb  and  Rollings  (23)  had  found  that  when  toluene 
was  passed  through  red  hot  coke  it  was  more  stable  alone 
than  in  the  presence  of  excess  hydrogen — that  is,  hydro- 
gen promoted  the  decomposition  of  toluene  into  benzene 
and  methane.  In  series  4  hydrogen  was  found  to  in- 
crease the  toluene  fraction  slightly.  Pure  toluene  was 
used  under  similar  conditions  and  found  to  be  somewhat 
more  stable  in  the  presence  of  hydrogen,  except  when 
the  furnace  was  in  the  activated  condition,  when  it  was 
entirely  decomposed  with  or  without  hydrogen. 

In  making  the  runs  with  naphthalene,  it  was  pre- 
heated in  an  electrically  heated  retort  connected  to  the 
upper  end  of  the  furnace.  The  naphthalene  vapors 
were  carried  into  the  furnace  by  means  of  the  gases 
which  were  bubbled  through.  It  was  noticed  that 
practically  as  soon  as  the  run  commenced  the  tempera- 
ture of  the  furnace  dropped.  Even  when  the  current 

[17] 


passing  through  the  heating  elements  was  materially 
increased,  the  temperature  fell  slowly.  This  would 
indicate  that  the  reactions  taking  place  inside  the  fur- 
nace were  absorbing  considerable  heat.  Another  fea- 
ture, particularly  noticeable  in  the  nitrogen  run,  was 
that  the  gas  recovered  did  not  equal  the  amount  passed 
into  the  furnace  from  the  cylinder,  even  with  the  addi- 
tion of  the  gas  from  decomposition  of  the  naphthalene. 
The  charcoal  may  be  partly  responsible  for  this  result. 

In  the  runs  using  carbon  dioxide  as  the  carrying  gas 
the  product  contained  a  heavy,  black,  high-boiling  oil, 
some  free  carbon  and  a  very  light,  fluffy,  red  material 
with  very  little  odor  of  naphthalene.  With  hydrogen 
the  product  was  dark  gray,  containing  also  traces  of 
the  light  reddish  material.  The  product  from  the  nitro- 
gen runs  was  a  compact  greenish  color  and  from  carbon 
monoxide  the  reddish  fluffy  material  formed  the  bulk 
of  the  recovery. 

The  bulk  of  the  recovered  product  was  naphthalene, 
with  small  amounts  of  benzerythrene  and  a-methyl-naph- 
thalene.  A  considerable  amount  of  /3-,8-dinaphthyl,  m.p. 
187-8  deg.  C.,  was  obtained  and  identified  by  the  picrate, 
m.p.  183  deg.  C.  The  a-a  and  a-/3  forms  were  present  in 
very  small  amounts. 

GASEOUS  PRODUCTS  SYNTHESIZED 

The  process  of  decomposition  of  hydrocarbons  can 
never  be  regarded  as  a  simple  effect  of  heat,  independ- 
ent of  contact  surfaces  and  the  gaseous  atmosphere  in 
which  it  is  conducted.  The  way  in  which  we  were  able 
to  modify  the  results  of  decomposition  in  various  direc- 
tions was  by  the  deliberate  control  of  these  two  factors. 
The  gaseous  products  obtained  in  these  experiments 
were  extremely  important  and  played  as  important  a 
part  in  the  final  products  as  the  gas  introduced.  Their 
effects  can  be  considered  from  two  standpoints — me- 
chanical and  chemical.  An  inert  gas,  like  nitrogen, 
would  not  enter  directly  into  chemical  reaction  under 
these  conditions,  but  would  play  a  very  important  part 
by  washing  the  products  of  decomposition  from  the 
surface  of  the  contact  material,  assist  their  volatiliza- 
tion by  lowering  their  concentration  in  the  vapor  phase, 
and  hurry  them  away  from  the  region  of  decomposition. 
In  the  case  of  hydrogen,  being  much  lighter,  it  has  a 
greater  diffusing  power,  the  molecules  travel  at  a  higher 
speed  and  thus  penetrate  small  areas  where  the  larger 

[18] 


gas  molecules  never  reach.  The  all-important  action  of 
hydrogen,  however,  is  chemical.  It  tends  to  reduce  the 
single  ring  benzene  hydrocarbons  to  benzene  itself.  A 
similar  action  may  be  inferred,  as  is  very  probable,  on 
the  attached  groups  of  more  complicated  ring  structures 
resulting  in  the  formation  of  naphthalene  and  anthra- 
cene. It  seems  that  this  was  the  part  played  by  hydro- 
gen in  the  majority  of  the  experiments  carried  out. 
However,  other  factors  must  be  able  to  modify  this 
tendency  of  hydrogen,  because  in  the  experiments  giv- 
ing the  largest  yields  of  the  toluene  fraction  it  was 
found  possible  to  increase  this  fraction  by  introducing 
hydrogen  from  a  cylinder.  It  was  possible  to  change 
the  production  of  hydrogen  in  these  experiments  by 
changing  the  temperature  or  the  activity  of  the  furnace. 

Methane  could  also  be  produced  in  varying  quanti- 
ties, depending  upon  the  furnace  conditions.  Bone  and 
Coward  (24)  concluded  that  methane  decomposes  chiefly 
directly  into  hydrogen  and  carbon,  the  process  being 
reversible  and  a  surface  phenomenon  at  least  up  to 
1,200  deg.  C.  At  the  temperature  these  experiments 
were  run  methane  is  practically  stable  and  its  chemical 
reaction  would  be  negligible,  but  its  mechanical  action 
would  be  very  important,  as  in  the  case  of  nitrogen. 

The  carbon  dioxide  formed  was  in  small  quantities 
and  was  always  in  equilibrium  with  carbon  monoxide. 
They  seemed  to  deaden  or  poison  the  activity  of  the 
furnace,  although  it  is  possible  C02  caused  partial  com- 
bustion. 

Acetylene  was  formed  in  small  quantities  and 
although  many  investigators  claim  that  the  building  up 
process  is  through  the  ability  of  acetylene  to  polymerize, 
it  was  concluded  from  these  experiments  that  acetylene 
played  a  very  small  part.  At  higher  temperatures  it 
was  more  likely  to  be  decomposed  to  carbon  and  hydro- 
gen than  to  be  built  up. 

ETHYLENE  FORMATION 

The  production  of  ethylene  in  these  reactions  was 
very  desirable,  because  it  was  noticed  that  wherever  the 
percentage  of  ethylene  in  the  outgoing  gas  approx- 
imated 3  or  4  per  cent,  the  yields  of  the  higher  boiling 
compounds  were  appreciably  increased.  In  general,  it 
was  found  that  ethylene  decomposed  into  a  mixture  of 
ethane  and  methane  in  the  neighborhood  of  500  deg.  C. 
Above  500  deg.  C.  the  ethane  content  gradually  de- 

[19] 


creased  and  around  650  deg.  C.  disappeared  entirely 
with  a  resultant  increase  in  methane.  Ethylene  seems 
to  be  able  to  decompose  in  several  ways,  which  no  doubt 
explains  its  usefulness  in  the  building  up  process. 

Bone  and  Coward  (24)  concluded  that  the  primary 
action  of  heat  on  ethylene  is  to  eliminate  hydrogen.  The 
residue  =CH  thus  formed  may  decompose  or  be  hydro- 
genated  to  methane,  or  it  may  unite  with  another  such 
residue  to  form  acetylene.  Hollings  and  Cobb  (23) 
found  that  at  lower  temperatures,  around  800  deg.  C.,  it 
decomposed  into  methane  and  acetylene,  while  at  higher 
temperatures  it  went  into  methane  and  hydrogen. 

In  some  of  these  experiments  as  high  as  15  per  cent 
of  the  waste  gas  was  found  to  be  ethane.  It  was  also 
found  that  very  little  ethane  was  formed  below  475  deg. 
C.  and  that  it  was  all  practically  decomposed  at  700  to 
725  deg.  C.,  except  in  the  presence  of  steam,  which 
seemed  to  stabilize  it  at  slightly  higher  temperatures. 
These  temperatures  are  far  lower  than  found  by  Hol- 
lings and  Cobb  (23),  who  found  that  the  decomposition 
of  ethane  was  rapid  but  not  complete  in  46  seconds  at  800 
deg.  C.  At  1,100  deg.  C.  only  88  per  cent  was  decom- 
posed, the  chief  products  being  ethylene  and  methane. 
No  doubt  the  molecular  decomposition  of  ethane  played  an 
important  part  in  these  experiments.  According  to  J.  J. 
Thomson  (25) ,  such  residues  as  ~CH,  =CH2  and  — CH3 
may  exist  momentarily  in  the  free  state.  The  four  possi- 
bilities open  to  the  residue  =  CH2  are :  (1)  To  form  ethyl- 
ene by  uniting  with  another  similar  residue ;  (2)  to  break 
down  into  carbon  and  hydrogen;  (3)  to  be  hydrogenated 
to  methane;  (4)  to  attach  to  some  heavier  molecular 
formation — a  partial  decomposition  of  the  benzene 
nucleus  or  homologs. 

The  above  is  only  a  partial  list  of  the  gaseous  con- 
stituents in  the  furnace  atmosphere  during  decomposi- 
tion; undoubtedly  many  more  complex  groups  or 
radicles  from  the  higher  boiling  compounds  exerted  an 
important  influence  on  the  decomposition  processes. 

LIQUID  HYDROCARBONS  IDENTIFIED 

Some  of  the  liquid  hydrocarbons  which  were  purified 
and  definitely  identified  by  physical  contents  or  known 
derivatives  are  listed  below.  Other  compounds  were 
obtained  but  have  not  been  identified. 

n-Hexane,  b.p.  68  deg.  C.,  was  obtained  in  the  ethylene 
series  of  runs  in  considerable  quantities  along  with  an 
un saturated  hydrocarbon,  which  had  very  similar  physical 

[20] 


properties,  probably  hexylene.  They  were  partly  separated 
by  the  usual  methods  and  the  last  traces  of  the  unsaturated 
compound  were  removed  by  selenium  oxych^ride.  This  re- 
agent reacts  top  violently  to  use,  however,  where  any  con- 
siderable quantity  of  the  unsaturated  compound  is  present. 

Cyclo  Hexane,  b.p.  80  deg.  C.,  was  obtained  in  small 
quantities,  and  after  a  partial  separation  from  benzene, 
was  purified  by  the  above  reagent.  However,  a  solution  of 
benzene  in  selenium  oxych'oride  will  readily  dissolve  cyclo- 
hexane.  In  cases  where  only  traces  of  benzene  were  pres- 
ent the  separation  was  rapid  and  complete. 

Benzene,  b.p.  80.5  deg.  C.,  was  obtained  in  several  runs. 
The  maximum  yield  obtained  was  93.0  per  cent  of  the  pos- 
sible theoretical. 

Toluene,  b.p.  110  deg.  C.,  was  obtained  in  many  of  the 
runs  over  charcoal.  The  maximum  yield  of  the  crude 
product  was  about  66.0  per  cent  of  the  possible  theoretical. 

a-  and  p-M ethyl-Naphthalenes,  b.p.  240-3  deg.  C.,  were 
identified  by  the  pier  ate,  m.p  112  deg.  C. 

Di-Tolyls  (mixed),  b.p,  275-8  deg.  C.,  were  identified  by 
the  acid  derivatives.  They  were  oxidized  by  prolonged 
boiling  in  chromic  and  glacial  acetic  acids. 

1. 2. Dimethyl-Naphthalene,  b.p.  262-4  deg.  C.,  was  iden- 
tified by  the  picrate. 

Diphenyl-E  thane,  b.p.  286  deg.  C.,  was  obtained  in  small 
quantities. 

SOME  OF  THE  SOLIDS  OBTAINED 

The  solids  synthesized  were  numerous  and  complex. 
In  a  single  series  of  runs  the  high-boiling  constituents 
were  very  similar,  but  in  different  series  the  variation 
was  marked.  In  the  series  using  cobalt  and  manganese 
the  high-boiling  oils  contained  a  larger  percentage  of 
solids  containing  anthracene.  The  partial  list  follows: 

Diphenyl,  m.p.  70  deg.  C.,  was  obtained  in  considerable 
quantities  in  the  fraction  boiling  from  340  to  255  deg.  C. 
On  standing,  it  settled  out  as  a  white  solid.  This  compound 
could  come  from  two  benzene  molecules  with  the  liberation 
of  hydrogen.  Dufton  and  Cobb  (18)  have  proved  this  to 
be  a  reversible  reaction  by  passing  diphenyl  and  hydrogen 
through  a  hot  silica  tube  and  producing  benzene. 

Naphthalene,  m.p.  80  deg.  C.,  was  obtained  in  considerable 
quantities,  as  closely  as  could  be  determined,  in  approxi- 
mately 4  per  cent  yields  on  the  original  xylene  used.  In 
view  of  the  conflicting  reports  in  the  literature  concerning 
the  formation  of  naphthalene  at  low  temperatures  and  from 
similar  liquids,  toluene  especially,  particular  care  was  taken 
in  the  purification  and  identification  of  this  compound.  The 
presence  of  stilbene  may  give  a  clue  to  its  formation. 

Phenanthrene,  m.p  98-100  deg.  C.,  was  obtained  in  small 
yields.  It  was  difficult  to  oxidize,  but  the  picrate  was  easily 
obtained. 

Stilbene,  m.p.  124  deg.  C.,  was  found  in  small  quantities; 
apparently  it  had  been  mostly  condensed  to  naphthalene. 

Pyrene,  m.p.  145-7  deg.  C.,  was  identified  by  the  picrate, 
m.p.  220  deg.  C. 

Methyl-Anthracene,  m.p.  200-5  deg.  C.,  was  obtained  in 
good  yields.  Both  alpha  and  beta  forms  were  present  and 

[21] 


Were  separated  by  means  of  the  methyl-anthracene-carbonic 
acids,  which  have  considerable  difference  in  the  melting 
point  temperature. 

p-Diphenyl-Benzene,  m.p.  207  deg.  C.,  was  also  formed 

Anthracene,  m.p.  212-14  deg.  C.,  was  formed  in  consider- 
able yields.  It  was  rather  difficult  to  purify  it. 

2.3.Dimethyl- Anthracene,  m.p.  244-6  deg.  C.,  was  puri- 
fied and  identified  by  the  quinone,  m.p.  180-2  deg.  C. 

Chrysene,  m.p.  248-50  deg.  C.,  was  obtained  in  small 
amounts  in  the  runs  with  ethylene  and  xylene  under  high 
pressures. 

Another  compound  which  has  been  separated  is  similar 
to  asphaltenes  in  its  appearance,  behavior  toward  solvents, 
especially  ether  and  hexane,  and  contains  sulphur.  Tht 
sulphur  must  have  come  from  the  contact  surfaces  inside 
the  furnace. 

SUMMARY  AND  CONCLUSIONS 

Some  of  the  more  important  results  as  indicated  by 
the  foregoing  investigation  are  given  in  the  following 
summary : 

1.  Mixed  xylenes  were  decomposed  by  heat  and  con- 
tact surfaces,  under  the  stabilizing  influence  of  hydro- 
gen and  methane,  almost  theoretically  into  benzene  and 
methane.     Sixty-nine  per  cent  of  the  original  xylene 
was  converted  into  crude  benzene,  which  boiled  below 
100  deg.  C.     This  is  approximately  94.0  per  cent  of 
the  possible  theoretical. 

2.  At  slightly  lower  temperatures,   under  the  same 
condition  of  contact  surfaces  but  in  a  gaseous  atmos- 
phere in  which  ethylene  greatly  predominated,  77  per 
cent  of  the  mixed  xylenes  were  built  up  into  higher 
boiling  compounds,  the  majority  of  which  were  solids 
at  ordinary  temperatures. 

3.  Mixed   xylenes,    under   other   conditions   of  tem- 
perature  and   contact    surfaces,    were    converted    into 
crude  toluene  in  quantities  approximating  64.0  per  cent 
of  the  theoretical. 

4.  Mixed  xylenes,  under  the  influence  of  heat  and 
iron    surfaces,    were    decomposed    quantitatively    into 
amorphous  carbon  and  gaseous  products.    Metallic  oxide 
surfaces,  especially  after  being  slightly  reduced  at  tem- 
peratures where  they  decompose  xylene  freely,  acceler- 
ate this  reaction.     Small  particles  of  iron  oxides  and 
reduced  iron  were  found  in  the  deposited  carbon. 

5.  The   reduced    metallic    surfaces,    or    freshly    oxi- 
dized surfaces  at  the  same  temperature  are  much  less 
reactive  and  tend  to  promote  partial  decomposition. 

6.  Non-metallic  substances  such  as  charcoal,  pumice 
or   refractory  material   at   like   temperatures   tend   to 

[.  22  1 


decompose  xylenes  into  unsaturated  and  higher  boiling 
compounds.  The  decomposition  to  carbon  is  materially 
lessened. 

7.  Activation    of  heated   iron   and  carbon    surfaces 
could  be  induced  by  treating  with  superheated  steam 
during  a  short  period  and  afterward  slightly  reducing 
with  hydrogen. 

8.  A  deadening  effect,  opposite  in  characteristics  to 
the   above,   was   caused   when   carbon   dioxide,   carbon 
monoxide,  air  or  superheated  steam  was  passed  through 
the  activated  furnace.    This  condition  seemed  to  be  the 
same,  as  is  ordinarily  described,  as  poisoning  of  the 
catalyzer.     Under   these   conditions   the   liquid   hydro- 
carbons were  most  stable. 

9.  Contact   surfaces   are  very   important   to   hydro- 
genation    and    dehydrogenation    of    aromatic    hydro- 
carbons. 

10.  The  gaseous  atmosphere  in  which  pyrogenic  de- 
composition takes  place  exerts  an  extremely  important 
influence  on  the  yields  and  products  of  decomposition. 
Gases  like  methane  and  nitrogen  between  temperatures 
of  600  to  700  deg.  C.  have  mostly  a  mechanical  action. 
Ethylene,  acetylene,  hydrogen  and  ethane  between  the 
same  temperatures  have  also  a  mechanical  bearing  on 
the  end  products,  but  their  all-important  action  is  chem- 
ical.    Ethylene,  acetylene  and  ethane  were  found  to  be 
entirely  decomposed  at  temperatures  above  725  deg.  C. 

11.  The    decomposition    of    ethylene    was    controlled 
so  that  practically  pure  methane  or  mixtures  of  methane 
and  ethane  were  obtained  as  end  products. 

12.  Pressure   under   some   conditions    favors    molec- 
ular condensation,  particularly  if  the  pressure  is  made 
up  of  unsaturated  gases.     In  other  cases,   where  the 
pressure  was  made  up  by  hydrogen,  it  caused  the  de- 
composition of  the   heavier  molecules   into   the   single 
ring  compounds.     Pressure   in   all   cases   lessened   the 
percentage   of   unsaturated   hydrocarbons   in   the   final 
products. 

13.  Decomposition    of    hydrocarbons    increases    with 
rise   in   temperature,    the   larger   molecules    being    less 
.stable  than  the  smaller  ones  at  temperatures  above  700 
deg.  C.     The  lower  the  temperature  at  which  decom- 
position takes  place  the  more  economical  the  reaction. 
Lower  temperatures   can   be   used   in   the   presence   of 
activated  surfaces. 

r  23  ;i 


BIBLIOGRAPHY 

7.  Bertholet,  M.,  Ann.  Chem.  Phys.,  Ser.  4,  t.9,  1866,  pp. 
445-483.       Ann.  Chem.  Phys.,  Ser.  4,  t.12,  1867,  pp.  5-96. 
Ann.  Chem.  Phys.,  Ser.  4,  t.16,  1869,  pp.  143-87. 

8.  Zanetti,  J.  E.,  and  Kendall,  M.,  J.  Ind.  Eng.  Chem., 
vol.  13,  1921,  pp.  208-11. 

9.  Zanetti,  J.  E.,  and  Egloff,  G.,  J.  Ind.  Eng.  Chem.,  vol. 
9,  1917,  p.  350. 

10.  Ferko,  Paul,  Ber.  Deut.  Chem.  Gesell.  Jahrg.,  vol.  29, 
Bd.  3,  pp.  660-4. 

11.  Haber,  F.,  Ber.  Deut.  Chem.  Gesell  Jahrg.,  vol.  29, 
Bd.  3,  p.  540. 

12.  McKee,  G.  W.,  J.  Soc.  Chem.  Ind.,  vol.  23,  1904,  p.  403. 

13.  Ipatieff,  V.  M.,  J.  Russ.   Chem.  Phys.  Soc.,  vol.  39, 
1907,  p.  681. 

14.  Ostromisslenski,   J.,    and    Burschanadse,   J.,   J.    Soc. 
Chem.  Ind.,  vol.  29. 

15.  Smith,  C.,  and  Lewcock,  W.,  J.  Chem.  Soc.,  vol.  101, 
pt.  2,  pp.  1453-59. 

16.  Rittman,  W.   F.,   Button,   C.    B.,   and   Dean,   E.   W., 
Bull.  114,  Bur.  of  Mines. 

17.  Charlton,  E.  E.,  Thesis,  University  of  Illinois,  1918. 

18.  Cobb,  J.  W.,  and  Dufton,  S.  F.,  Gas  World,  vol.  72, 
1920,  p.  485. 

19.  Parr,  S.  W.,  and  Olin,  H.  E.,  Bull.  79,  U.  of  I.  Eng. 
Expt.  Station. 

20.  Parr,  S.  W.,  and  Layng,  T.  E.  L.,  45,  U.  of  I.,  1916. 

21.  Clark,  J.  M.,  J.  Ind.  Eng.  Chem.,  vol.  11,  No.  3,  1919, 
p.  204. 

22.  Cook,  O.  W.,  and  Chambers,  V.  J.,  J.  Ann.  Chem.  Soc., 
vol.  43,  No.  2,  1921,  p.  334 

23.  Cobb,  J.  W.,  and  Rollings,  H.  S.,  J.  Gas  Lighting,  vol. 
126,  p.  917. 

24.  Bone  and  Coward,  J.  Chem.  Soc.,  1917,  vol.  93,  p.  1908. 

25.  Thomson,  J.  J.,  Chemical  News,  1911,  vol.  103,  p.  265. 

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Contribution  from  the  Chemical  Laboratories, 

University  of  Illinois. 
Urbana,  111. 


[24] 


VITA 

The  writer  of  this  thesis  received  his  early  education  in  the 
grade  school  at  Leskard,  and  high  school  at  Bowmanville,  Ontario. 
He  entered  McMaster  University  in  the  fall  of  '09  and  graduated 
with  the  degrees  of  Bachelor  of  Arts  in  the  honor  science  course, 
and  Master  of  Arts  in  Chemistry  in  1915. 

After  graduation  he  entered  war  munition  work.  From  Sep- 
tember, 1915,  to  March,  1916,  analyzing  high  explosives  at  the  plant 
of  The  Canadian  Explosives,  Ltd.,  Montreal.  From  March,  1916, 
to  November  of  the  same  year  analyzing  9.2  inch  shell  steel,  at 
the  plant  of  the  Canada  Cement  Co.,  Montreal.  During  November 
he  was  at  the  plant  of  the  Armstrong- Whithworth  Co.,  Longuiel, 
Quebec,  analyzing  tool  steel.  From  December,  1916,  to  October, 

1917,  he  was  with  the  British  Munitions  Board,  stationed  at  the 
acetone  plant  of  the  Canadian  Products    Co.,    Shawinigan    Falls, 
Quebec. 

Since  October,  1917,  he  has  been  at  the  University  of  Illinois 
doing  graduate  work.  While  here  he  has  held  the  following  posi- 
tions in  the  Department  of  Chemistry:  October,  1917,  to  February, 

1918,  graduate  assistant;  and  from  February,  1918,  to  the  present 
time,  half-time  assistant. 


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